Integrated circuit (IC) test socket with Faraday cage

ABSTRACT

An integrated circuit test socket includes a highly conductive compliant material that is cut and installed into the test socket. The conductive material draws electrical charge away from the test socket, leading to more accurate testing. The test socket base is grounded, and a ground current runs through the base and into conductive strips. The configuration forms an electromagnetic impulse shield, protecting the chip from electromagnetic interference. The compliance of the shield material allows the shield to be sealed when activated, ensuring that the electromagnetic impulse shield is complete around the semi-conductor chip.

BACKGROUND

The present invention relates to sockets that electrically connects anintegrated circuit with an IC board. More particularly, the presentinvention is directed to a test socket for testing an integratedcircuit, wherein the test socket is enclosed in a conductive structurethat acts as a faraday cage to eliminate noise and interference duringthe testing of an IC chip.

Integrated circuit tester devices have long been used in thesemiconductor industry to test and evaluate the quality of the chips offthe manufacturing line. Signal integrity is a critical aspect of chipdesign and testing. To this end, it is desirable to maintain impedancethrough a conducting portion of a contact interconnecting the integratedcircuit lead to its corresponding load board pad at a particular desiredlevel. The effective impedance of the design is a function of a numberof factors. These include width and length of conduction path, materialof which the conductive structure is made, material thickness, etc.

When testing the electrical characteristics of a packaged or moldedsemiconductor device such as an integrated circuit (IC), it is common toutilize a specialized test socket that secures and connects the IC tothe equipment that evaluates its performance, i.e. a handler and a loadboard. Many different test sockets have been devised for quickly andtemporarily connecting integrated circuit leads of a chip to be testedto a load board of a tester. Automated test apparatus in particular usea number of such sockets. Typical socket arrangements use force broughtto bear upon a contact positioned between a lead of the IC and the loadboard to deform a probe tip of the contact and engage a pad on the loadboard. Such a configuration provides for positive connection between thepins or contact pads of the DUT and corresponding leads of a testapparatus. Examples of this type of connection can be found, forexample, in U.S. Pat. No. 6,409,521 to Rathburn, and U.S. Pat. No.7,737,708 to Sherry, the teachings and contents of both of which arefully incorporated herein by reference.

U.S. Pat. No. 7,918,669, the contents of which are incorporated hereinby reference, is a test socket devised by the present inventor. Thesocket of the '669 patent uses a unique linkage to urge the connectorsof the test circuit upward where it can make contact with the testequipment. This test socket was found to be very successful in ensuringgood contact with the test apparatus while reducing force on the circuititself. A component of that test socket was an elastomer element thatprovided a resiliency to the link, ensuring proper contact in a costeffective and reliable manner. The cylindrical elastomer keeps thecontact links in place, and their resiliency acts like a springmechanism for the links. This allows for vertical movement on the link.

When such test sockets are used, it is common for small amounts ofstatic charge to build up on the socket, which can affect the results ofthe testing. Charged test sockets can transfer their charge to thecircuit under test, which then leads to noise being introduced into thetesting. Noise in the testing impairs the ability of the tester toevaluate the integrated circuit properly. Accordingly, the presentinvention is designed to reduce or eliminate the build-up of electricalcharge on the test socket, leading to more accurate test results.

SUMMARY OF THE INVENTION

The present invention is directed to an integrated circuit test socketthat includes a highly conductive compliant material that is cut andinstalled into the test socket. The conductive material draws electricalcharge away from the test socket, leading to more accurate testing. In apreferred embodiment, the test socket base is grounded, and a groundcurrent runs through the base and into conductive strips. Theconfiguration forms an electromagnetic impulse shield, protecting thechip from electromagnetic interference. The compliance of the shieldmaterial allows the shield to be sealed when activated, ensuring thatthe electromagnetic impulse shield is complete around the semi-conductorchip.

These and many other features of the present invention will best beunderstood by reference to the following descriptions and figures.However, it is to be understood that while the inventor's best mode hasbeen described and shown, the invention is not to be limited to anyparticular drawing or description. Rather, it is understood that theremay be many variations of the present invention that would be readilyappreciated by one of ordinary skill in the art, and the inventionencompasses all such variations and modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated, perspective view of an embodiment of the testsocket and testing apparatus;

FIG. 2 is a side view of the socket and testing apparatus of FIG. 1;

FIG. 3 is a top view of the test socket of FIG. 1; and

FIG. 4 is a bottom view of the test socket of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate an integrated circuit test socket 20 of thetype generally described in U.S. Pat. No. 7,918,669, the contents ofwhich are incorporated herein. The details of the test socket is omittedherein for brevity. The test socket base 20 has a generally squareprofile with four aligning holes 22 to mount the socket base on thetesting equipment. On a lower surface 28 of the base 20, a set of pegs30 may be used to further align and set the base on the test equipment.On an upper surface 24 of the test socket base 20 (see FIG. 3), a squarerecess 26 is formed to receive the integrated circuit chip (not shown)under test. A plurality of electrical connectors are formed within therecess 26 as described more fully in the patent referenced above. Oncethe integrated circuit is placed in the recess, the test socket base 20may be placed, for example, in a handler work press 32 and clamped inthe handler 32 in anticipation of testing the integrated chip. Thehandler/work press 32 utilizes a clamping plate 34, where the clampingplate 34 encloses the chip under test. Other arrangements, bothautomated and manual, are also possible with the present invention.

A Faraday cage is a container or enclosure made of conducting material,such as wire mesh or metal plates, that shields what it encloses fromexternal electric fields. In chip testing, static charge on the socketand surrounding elements generate external electromagnetic interference(EMI, or noise) that can interfere with the test results. The presentinvention forms a Faraday cage around the chip under test to shield thechip from EMI and noise during the testing.

Turning to FIG. 3, an EMI shield 40 is formed on the socket base 20 suchthat it is wedged between the base 20 and the clamp plate 34. The shieldis made if a conductive material and may be a mesh or solid thin plate.The cage may be adhered to the top surface 24 of the base 20 byinsertion into a groove, by adhesive, by fastener, or by other means.

FIG. 4 illustrates the bottom surface 28 of the socket base 20,including the test socket 42 connected to four diagonal members 46. Thefour diagonal members 46 on the bottom of the base 20 make contact withthe printed circuit board. The corresponding paths on the printedcircuit board are grounded. This ground current runs through the baseand into the EMI shield. The shield serves as a mini-faraday cage forthe device, shielding the device with the conductive socket shieldgrounded to the printed circuit board.

The conductive shield 40 is preferably formed as part of the socket base20. In other words, the socket may be constructed to include the shield40, the chip test socket 42, and the base 20 as a single piece, andtogether these components cooperate to constitute the integrated shield.Further, the contact footprint of the socket base 20 to the printedcircuit board is defined by the grounding requirements of theapplication.

The shield 40 can be constructed of four discrete plates 40 a or meshesthat are placed in a recess sized to hold the plates. The four plates 40a cooperate to form an octagon above and around the square recess 26, sothat the clamp 34 contacts the upper surface of the shield 40.

It will be understood that this disclosure is merely illustrative, andthat it is to be further understood that changes may be made in thedetails, particularly in matters of shape, size, material, andarrangement of parts without exceeding the scope of the invention.Accordingly, the scope of the invention is as defined in the language ofthe appended claims, and is not limited in any manner by theaforementioned descriptions and drawings.

I claim:
 1. A test socket for a microchip, comprising: a base includinga plurality of aligning through holes for securing the base to ahandler, the base further comprising a chip test socket and a shieldcomprising four adjoining plates surrounding the test socket, each plateincluding a pair of edges aligned parallel to the test socket and a pairof edges aligned diagonally to the test socket; wherein the shield isentirely disposed on top of the base and is sandwiched between the baseand a clamp plate when placed in a tester; and wherein the base, shield,and test socket are integrated as a single unit.
 2. The test socket ofclaim 1, wherein the shield is octagonal shaped.
 3. The test socket ofclaim 1, wherein the shield is made of a metal mesh.
 4. The test socketof claim 1, wherein the base and the shield form a Faraday cage aboutthe microchip when the base is seated on a grounded circuit board.